Ignition means for gas heaters



Nov. 12, 1940. R BETZ 2,221,667. IGNITION MEANS FOR GAS HEATERS FiledAug. so, 1955 TO CONTROL SYSTEM I E l EC TRICA LLLOPERATF 0 VA l-VEELECTRICALL! ERA 'ED VALVE l WW E 60 J9 ZSmaentor Patented Nov. 12, 1940PATENT OFFICE IGNITION MEANS FOR GAS HEATERS Paul L. Betz, Baltimore,Md., assignor to Consolidated Gas Electric Light and Power Company ofBaltimore, Baltim Maryland ore, Md., a corporation of Application August30, 1935, Serial No. 38,655

12 Claims.

This invention relates to safety devices for gas heaters of the typeprovided with a pilot for igniting the main burner or burners when gasis supplied to the heater.

Gas heating systems, such as for example the conventional type of gaswater heater, usually include means to ignite the gas at the main burneror burners whereby the operation of the system may be initiated merelyby turning on the gas, either automatically or manually. These means maycomprise either gas flames or electric ignition devices such asincandescent wires. In connection with such systems, it is desirable toprovide a safety device such that the supply of gas to the main burnercannot be turned on unless the pilot is in condition to function prop-'erly in igniting the main burner. For example, it has been proposedheretofore to provide an electromagnetically operated safety valve to-One of the objects of this invention is to provide a novel safety devicein combination with the pilot of a gas heater and adapted to insure 35valve in the event that ating condition.

Another object is to provide novel thermally responsive means incombination with the pilot of a gas-heater and constituting therewith asafety device to prevent operation of the heater unless the pilot is inoperating condition which means will not be materially affected by heatfrom sources other than the pilot.

A further object is to provide a novel device of the type characterizedabove which is light, small and compact and inexpensive but at the sametime reliable and dependable in operation.

A still further object is to provide a safety device of the typecharacterized above which if desired can be assembled with an electricpilot as a unit and can also be restored or replaced as a unit.

While a pilot in the form of a gas flame ordif narily burnscontinuously, an electric ignition the pilot is not in opergether with athermocouple'subjected to the heat closing or to prevent opening of agas supply.

device or pilot may readily be adapted for energization only during theoperation of the burner,

or if desired for deenergization immediately following the ignition ofthe burner so that it is used only during the ignition period, withresultant decreased current consumption, economy and longer life.Further objects of the invention are to provide novel electrical controlsystems particularly adapted for the operation and control of anelectric pilot and its associated safety device as characterized above,whereby'the pilot is operated only during operation of the heater andwhereby the pilot current can be reduced following the ignition of themain burner, without interfering with the safety functions of saiddevice.

The invention is illustrated in the accompanying drawing, but it is tobe expressly understood that said drawings are for purposes ofillustration only and are not to be construed as a definition of thelimits of the invention, reference being had to the appended claims forthis purpose.

In the drawing: Fig. 1 is a perspective view showing an apparatusembodying the invention which for purposes of illustration is associatedwith a conventional form of gas burner;

Fig. 2 is a sectional view of the device shown in Fig. 1; and

Figs. 3 and 4 illustrate two suitable control systems which may beemployed in connection with a device of the type shown in Figs. 1 and 2.In Figs. 1 and 2, a combined electric pilot and associated safety deviceis shown in association with a portion of a gas burner I of aconventional type having a plurality of ports 2, this type of burnerhaving sector-shaped openings 3 therein. As shown in Fig. 1, thecombined pilot and safety device is disposed in one of these openingsand two of the adjacent ports 2 are provided with pipes 4 which directgas toward the pilot device to facilitate ignition of the gas. It willbe understood, however, that the invention is not limited to thisparticular manner of installation and use of the device.

As shown in Figs. 1 and 2, the pilot comprises a coil of wire 5 which isadapted to become incandescent on passage of current to provide for theignition of gas from the pipes or nozzles d. The coil 5 is connected atits endsto terminal strips 6 whereby current is conducted to and fromthe coil. This coil is mounted on a suitable base 1 by means of platesor blocks 8 assembled on the base in any suitable manner as by screws 9.Preferably blocks 8 are of metal and the terminals 6 are insulatedtherefrom in any suitable manner as by interposed strips of mica orother insulating material.

Associated with the coil 5 is a safety device comprising two similarthermally responsive elements so disposed that with respect to ambientheat their response is equal and similar with no relative movementbetween them, but arranged so that one of them is more affected by heatfrom said coil than the other. The thermally responsive elements in theform shown comprise two bimetallic strips I0 and II which are supportedat their ends between the blocks 8 and insulated therefrom as describedabove. The bimetallic strips I8 and II respectively carry contacts I2-and I3 and said strips are: so arranged that these contacts are normallyseparated. The two bimetallic strips are arranged to.bend in the samedirection and to substantially the same extent under the same change oftemperature so that any bending of the strips occurring as the result ofequal changes in temperature of the two strips does not result in theclosing of the contacts. Thus changes of temperature in the surroundingair, which affect both strips equally, do not result in closing thecontacts. However, the adjacent strip I8 receives more heat from thecoil 5 than the strip I I with the result that the deflection of stripI0 is greater than that of strip II, causing the contacts to close whenthe pilot coil is energized. As soon as the coil cools off, thebimetallic strips return to normal positions and contacts I2 and I3 areagain opened. Preferably the safety device is suitably. shielded fromair currents about the burner and through the opening 3 so that itsoperation is not affected thereby.

Devices embodying the invention can be employed in any suitable way tocontrol electrically either a special safety valve or the usualautomatically operated supply valve of a gas heating system, it beingnecessary only to make the proper circuit connections to the contacts I2and I3, which connections can be varied depending upon the type ofcontrol system and valve that is employed. When so connected, theinvention provides an electric pilot or ignition device which operatesreliably and dependably but in the event of failure of the pilot toreach ignition temperature for any reason,- such as an open circuit, thesafety feature is automatically provided by failure of the contacts I2and I3 to close. The invention provides an additional advantage in thatthe safety device prevents opening of the gas valve until the pilot coilhas reached the desired operating temperature, thus preventing the flowof gas during the brief period in which the pilot is heating up toignition temperature and the consequent danger of explosion.

While devices embodying the invention can be used in association withany suitable control circuit, in many cases it is desirable to provide acontrol system such that the safety contacts are opened after the gas isignited and while it continues to burn. Forexample, assuming that thesafety contacts remain closed during the operation of the heater, if thecontrol system is deenergized for any reason the gas is shut off andthe.

pilot cools very rapidly, but the bimetallic operating members for thesafety contacts may cool more slowly and the contacts may not openimmediately. If the control system is again energized and the gas isturned on under this. condition, the heater may become filled with gasbefore the pilot has time to reach ignition temperature with consequentdanger of an explosion. Hence it is desirable to connect the pilot andsafety contacts in a-circuit controlled by a suitable relay in such away that the gas cannot be turned on until the safety contacts close,but after the operation of the system is initiated, the safety contactsare permitted to open so as to be ready for another cycle withoutinterrupting the operation of the system.

Fig. 3 illustrates a control system whereby op- .eration as abovedescribed can be provided.

Current is supplied to the system through leads I4, a control switch I5and a transformer I6. A pilot device such as that described above isshown diagrammatically and comprises a pilot coil I8 and thermallyoperated contacts I9 and 20 which are normally open as shown but adaptedto be closed when the pilot coil I8 reaches ignition temperature. Thepilot coil I8 is connectedat one end to the secondary of the transformerI6 by wires 2| and 22 and at the other end in series with a resistance23 and a resistance 24 which is preferably a second pilot coil andthence through wires 25 and 26 to the transformer secondary. A relay 21of any suitable type is arranged normally to hold the bridging arm 28across contacts 29 and 30, thereby short-circuiting resistance 23 bymeans of wires 3I and 32. One terminal of the relay 21 is connected tothe transformer secondary through wires 26 and 33 and the other terminalis connected to the other side of the transformer through wires 34, 35,36 and 22, this circuit including. contacts I9 and 28. An electricallyoperated gas supply valve of any suitable type is shown at 31, thisvalve being connected to Wires 26 and 34 in parallel with therelay 21.

When the control switch I5 is closed, current passes through wires 22and 2| and pilot coil I8, then through wire 3|, arm 28 and wire 32 inparallel with resistance 23, and then through pilot coil 24 and wires 25and 26. At this time the relay 21- and the valve 31 are not energized asthe contacts I9 and 28 are open. When the coils I8 and 24 reach ignitiontemperature, contacts I 9' and 28 close and valve 31 opens to supply gasto the burner. At the same time relay 21 is energized and shiftsbridging arm 28, opening the circuit between contacts 29 and 30 while atthe same time. closing the circuit between contacts 29, 38 and 39. Thisoperation does not deenergize the relay 21 or valve 31, and itestablishes the circuit between wires 34 and 22 by way of wire 40,contact 39, arm 28 and contact 38 in parallel with the circuit throughwire 35, contacts I9 and 20 and wire 36. At the same time the arm 28, bybridging contacts 38 and 29, establishes a shortcircuit around pilotcoil I8 by way of wire 22, arm 28 and wire 3|. Current then passesthrough wire 22, arm 28 and wire 3|, and thence through resistance 23,pilot coil 24 and wires 25 and 26. Pilot coil-24 therefore remainsheated, but as the coil I8 cools 01! due to the reduction in currentflow, contacts I9 and 20 open without affecting relay 21 or valve 81. Assoon as the switch I5 is opened, however, valve 31 closes and relay 21restores the arm 28 to its original position so that the system is readyfor another operation.

During the initial ignition period, the resistance in the pilot circuitbetween wires 22 and 26 includes the resistance of pilot coils I8 and24, resistance 23 being short-circuited. As the two pilot coils I8 and24 are preferably substantially similar, they both become heated toignition temperature by the time that contacts I 9, 20 close and the gasis turned on. Then on operation of the relay and gas valve the pilotcoil I8 is short-cit cuited so that it cools off and contacts 19, 20open so that they are ready for another cycle of operation. However,pilot coil 24 remains energized and inoperating condition as long as thecontrol system is energized. If resistance 23 has the same value as theresistance of pilot coil IS, the

current through pilot coil 24 is the same both before arid after theoperation of the relay. It

will be seen that it is not essential that coil I8 be a pilot coil butthis is preferable in order that the element which is associated withthe safety contacts shall be in condition to insure ignition of theburner before the safety contacts are closed.

If the resistance 23 is of greater value than coil l8, the currentconsumption after the ignition period can be reduced substantially toany extent while at the same time the coil l8 cools off, thus reducingcurrent consumption and resulting in increased economy of operation andlonger life of the pilot coil. The reduction in pilot cur rent may beproportioned to leave the pilot 24 at a temperature sufiicient to ignitethe. gas in the event of momentary interruption of the gas supply forany reason, the initial high pilot temperature'insuring ready ignitionin normal operation, or the current may be further reduced to anydesired extent. In this case, however, it is desirable to provide foropening the gas valve shortly before the relay operates, in view of thefact that the pilot current is decreased at this time. This can readilybe accomplished, for example, by employing a relay of any known typewherein the operation of the relay contacts is delayed for an intervalafter energization of the relay, which will not change the pilot circuituntil a suitable interval has elapsed after the gas valve is opened.Various types of relays having time delayed operation are known, and arelay suitable for this purpose is shown in U. S. Patent No. 2,087,216of Paul L. Betz issued July 13, 1937.

It will be perceived that the system as described above can beassociated with other safety devices 45 and automatic controls which areadapted to prevent the operation of valve 31 or to close said valve inthe event of flashback or excessive temperature, etc. Since the detailsof such devices constitute no part of the present invention, they 50 arenot shown herein. Such devices may be connected with the system abovedescribed in any suitable way which does not interfere with the intendedoperation thereof, as for example at the point indicated in the wire 26by the words To 55 control system.

Fig. 4 illustrates another control system which can be employed. Thecurrent flowing through the pilot coil is discontinued after the gas hasbeen ignited, but with a single pilot coil. In

60 this system current is supplied to the transformer 4| by the leads 42and control switch 43. The electric pilot coil 44 is connected at oneend to the transformer secondary by wires 45 and 46 and at the other endby wire 41 with a contact 65 48. The bridging arm 49 normally connectscontact 48 with contact 50 whereby the circuit through the pilot coil iscompleted to the other side of the transformer secondary through wires5| and 52.

70 has one terminal connected to wire 52 and the other terminalconnected to a wire 54 which leads to one of the contacts 55 of a safetydevice associated wtih the pilot coil 44, the other contact 55 beingconnected by wires 51 and 46 to the 75 transformer secondary. A relay 58having time The electrically operated valve 53 delayed operation of anysuitable known type,

such as that shown in the Betz patent referred to above, is connectedacross wires 52 and 54 in parallel with the valve 53, this relaynormally maintaining the bridging arm 49 inc. position relay 58 are openbecause the contacts 55, 56 are open, but the circuitof pilot coil 44 isclosed as described above. The coil, therefore, heats up to ignitiontemperature and causes contacts 55, 56 to close, thereby energizing thevalve 53 and relay 58. Valve 53 immediately opens supplying gas to theburner to be ignited by the pilot 44. The operation of relay 58,however, is delayed for an interval sufficient to insure ignition of thegas, and thereafter the relay operates to swing the arm 49 -to-itsopposite position. This operation of the relay is utilized to interruptthe current to the pilot coil 44 by opening the circuit between arm 49and contact and to establish a short-circuit in parallel with thecontacts 55 and 56 by way of wire 46, contact 59, arm 49, contact andwire 6|. The interruption of the current through the pilot coil causesthe pilot coil to cool thereby permitting contacts 55, 56 to open. Thisdoes not, however, affect the valve 53 nor the relay 58 because thecircuits of the same are completed by way of wire 54, wire 6|, contact60, arm 49, contact 59 and wire 46. The system, therefore, continues tooperate until the valve and relay are deenergized as by opening theswitch 43 or by the operation of any suitable control devices which maybe employed. In this eyent,-valve 53 closes and the relay 58 returns thearm 49 to its initial positionv whereby the system is ready for furtheroperation in the manner described above.

While the use of the relay 58 as shown in Fig. 4 is generally desirabletogether with the contacts 55 and 56, the latter of themselves providethe safety feature that the valve cannot be opened until the pilotdevice reaches ignition temperature, and this function is normallyaccomplished independently of the relay operation and hence for somepurposes the contacts may be used alone and the relay omitted.

It will be seen from the foregoing description that the inventionprovides a combined electric pilot and safety device which is small andcompact and relatively inexpensive and which, if desired, may constitutea unit for installation or replacement. With respect to the safetydevice, the use of two thermally actuated devices which respond equallyand in the same direction in the event of equal changes of temperatureprovides for safety operation that is substantially independent of allheat affecting both devices to the same extent. Hence, when the deviceis properly installed, it is inoperative except in response to heat fromthe pilot itself, but is reliable and dependable in performing itsintended function as a safety device. The combined electric pilot andsafety device is particularly adapted for use in electrical controlsystems such' as those described above, wherein the contacts act as asafety device to prevent opening of the gas valve until the pilotreaches ignition temperature, but then after being closed to effectopening of the valve and turning on of the gas, are opened while theburner continues in service. Thus, the safety device is restored tonormal condition and is ready for the next cycle of operation in con--dition to accomplish its intended function. Further, current consumptioncan be reduced and greater economy of operation obtained without in anyway interfering with the accommplishment of the safety function.

While the invention has been described and illustrated in the drawingswith particularity, it will be understood that the invention is notrestricted to the embodiments so described andillustrated, but changesmay be made in the form, details of construction and arrangement of theparts and in the circuits employed without departing from the spirit ofthe invention. Reference is, therefore, to be had to the appended claimsfor a definition of the limits of the invention.

What is claimed is:

1. In an electrical ignition system for a gas burner, the combination ofan electrically operated valve, a valve circuit including valveoperating means and a pair of normally open contacts, a circuitincluding an electric pilot and an impedance, means responsive to heatfrom said pilot for closing said contacts, a circuit in parallel withsaid pilot, a circuit in parallel with said impedance, a circuit isparallel with said normally open contacts and relay means energizedsimultaneously .with the closing of said contacts for completing saidfirst and last named parallel circuits and for opening. said secondnamed parallel circuit.

2. In an electrical ignition system for a gas burner, the combination ofan electrically operated valve, a valve circuit including valveoperating means and a pair of normally open-contacts, a circuitincluding an electric pilot and an impedance, means responsive to heatfrom said pilot for closing said contacts, a circuit in parallel withsaid pilot, a circuit in parallel with said impedance, a circuit inparallel with said normally open contacts, and relay means having timedelayed operation energized simultaneously with the closing of saidcontacts for closing said .first and last named parallel circuits andfor opening said second named parallel circuit.

3. In an electrical ignition system for a gas burner, the combination ofan electrically operated valve, a valve circuit including means foroperating said valve and a pair of normally open contacts, a circuitincluding an electrical pilot device, thermally responsive means subjectto heat from said pilot device to close said normally open contacts, acircuit in parallel with said pilot device and including a pair of relaycontacts, a relay for closing said relay contacts, and a relay circuitincluding said normally open burner, the combination of an electricallyoperated valve, an operating circuit including valve operating means,relay means having time delayed operation, anda pair of normally opencontacts, a circuit including an electric pilot, means responsive toheat from said pilot for closing said contacts, a circuit in parallelwith said pilot,

a circuit in parallel with said normally open contacts, and meansoperated by said relay means for closing said parallel circuits.

6. In an electrical ignition system for gas burners, the combination ofan electrically operated valve, a relay, an operating circuit includingmeans for operating said valve and said relay and a pair of normallyopen contacts, a circuit including two electric pilots, thermallyresponsive means operated by one of said pilots for closing saidcontacts, and a circuit having relatively low resistance in shunt withsaid one pilot and including circuit closing means operated by saidrelay.

'7. In an electrical ignition system for gas burners, the combination ofan electrically operated valve, a relay having time delayed operation,on operating circuit including means for operating said valve and saidrelay and a pair of normally open contacts, a circuit including twoelectric pilots, thermally responsive .means operated by one of saidpilots for closing said contacts, and a circuit having relatively lowresistance in shunt with said one pilot and including circuit closingmeans operated by said relay.

8. In an electrical ignition system for a gas burner, the combination ofan electrically operated valve, a relay, an operating circuit includ--ing means for operating said valve and said relay and a pair of normallyopen contacts, a circuit including in series two electric pilots and aresistance, thermally responsive means operated by one of said pilotsfor closing said contacts, two circuits one of which is in parallel withsaid one pilot and the other with said resistance and each of whichincludes relay contacts, said relay being adapted to normally close thecircuit in parallel with said resistance and on operation of saidnormally opeh contacts to open the circuit in parallel with saidresistance and to close the circuit in parallel with said pilot.

9. In an electrical ignition system for a gas burner, the combination ofan electrically operated valve, a relay, an operating circuit includingmeans for operating said valve and said relay and a pair of normallyopen contacts, a circuit including in series two electric pilots and aresistance, thermally responsive means operated by one of said pilotsfor-closing said contacts, two circuits one of which is in parallel withsaid one pilot and the other with said resistance and each of whichincludes relay contacts, said relay being adapted to normally close thecircuit in parallel with said resistance and on operation of saidnormally open contacts to open the circuit in parallel with saidresistance and to'close the circuit in parallel with said pilot, saidresistance being substantially equal to the resistance of saidone'pilot.

10. In an electrical ignition system for a gas burner, the combinationof an electrically operated valve, a relay having time delayedoperation, an operating circuit including means for operating said valveand said relay and a pair of normally open contacts, a circuit includingin series two electric pilots and a resistance, thermally responsivemeans operated by one of said pilots for closing said contacts, twocircuits one of which is in parallel'with said one pilot and the otherwith said resistance and each of which includes relay contacts, saidrelay being adapted to normally close the circuit in parallel with saidresistance and on operation of said normally open contacts to open thecircuit in parallel with said resistance and to close the circuit inparallel with aaaacer said pilot, said resistance being greater than theresistance of said one pilot.

11. In an electrical ignition system for a gas burner, the combinationof an electrically op erated valve, a valve operating circuit includinga pair of normally open contacts, a circuit including two electricpilots and a resistance in series, means responsive to heat from one ofsaid pilots to close said contacts, a low resistance circuit in parallelwithsaid resistance, a low resistance circuit in parallel with said onepilot, a circuit in parallel with said contacts, a relay circuitenergized upon closure of said contacts, and. relay means for openingsaid first parallel circuit and closing said other parallel circuits.

12. In an electrical ignition system for a gas burner, the combinationor an electrically operated valve, a valve operating circuit including apair of normally open. contacts, a circuit including two electric pilotsand a resistance in series, means responsive to heat from one 01' saidpilots to close said contacts, a low resistance circuit in parallel withsaid resistance, a low resistance ciredit in parallel with said onepilot, a circuit in parallel with said contacts, a relay circuitenergized upon closure of said contacts, and relay means for openingsaid first parallel circuit and closing said other parallel circuits,said resistance being greater than said one pilot and said relay meanshaving time delayed operation.

PAUL L. nnrz.

